Spray booth

ABSTRACT

A spray booth is equipped with an air-exhaust system and a highvolume low-pressure water circulating system moving the water from a settling sump to troughs supplying water-curtain panels providing water screens along lines of drainage. The water is pumped by a water lift open to local atmospheric pressure. The configuration of the booth provides for accepting spray gun equipment in the form of replaceable modules. One form of these modules includes a spray gun carriage having a linear path of movement induced by a differential chain drive.

United States Patent 1191 Szczepanski May 28, 1974 [54] SPRAY BOOTH 3,680,784 8/1972 Fakes 239/126 1 755 kl h [76] or 3 3:23 3: elg Primary ExaminerLloyd L. Kmg

Attorney, Agent, or FirmGlenn B. Morse [22] Filed: Oct. 16, 1972 [21] Appl. No.: 297,666 ABSTRACT A spray booth is equipped with an air-exhaust system [52] U S Cl 239/193 and a high-volume low-pressure water circulating sys- 51] 161:0. i 1905b 1/36 moving the water a Settling Sump troughs 158 Field 61 Search 239/126, 127, 185, 186, supplymg F Panels P Water 239/209 193 134/198 199 200 screens along lmes of dramage. The water 1s pumped by a water lift open to local atmospheric pressure. The [56] References cued configuration of the booth provides for accepting spray gun equipment in the form of replaceable mod- UNITED STATES PATENTS ules. One form of these modules includes a spray gun 1g; l f l? carriage having a linear path of movement induced by ngaitc e r v 3,556,402 1/1971 Wolking 1 239/126 a dlfferentla] cham dnve' 3,606,159 9/1971 Sutton 239/127 15 Claims, 34 Drawing Figures ?MENTEBMMZMH 3L813L042 sum 02 or w Fig. 3

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Pmminms 1974 331304 sum ma 0% IIL IllI!!!III!IIIIIIIIIIIIIIIIIIIIIIII PATENTED 1m 28 1974 saw as ar14 F/ l i4 PATENTEDWZB I51 I 33313042 sum 7106i 14 PATEN'SEMmzsmu $813042 sum "12 of 14 III/1111111- PATENTEDmzemn 3.81.3; SHEEI im or w 042 SPRAY BOOTH BACKGROUND OF THE INVENTION The application of sprayed coating material as an industrial process normally involves the use of a spray booth, which is a structure having two primary functions. One of these is the removal of vapors associated with sprayed materials, and the other is the retrieval of sprayed particles that are not impinged on the work pieces. The retrieved material may either be salvaged, or collected preparatory to dumping or clean-out. The collection of these particles is normally performed by curtains of water cascading down over panels defining the boundaries of the work area exposed to sprayed material. Water is conventionally supplied to these panels by providing spray nozzles or distribution troughs along the upper margins of the panels, with these being fed by closed piping systems extending from positive-displacement pumps. The conventional arrangements have generated a number of problems. Piping mounted within the booth structure is of necessity installed where working space is severly limited, and exterior piping takes up extremely valuable floor space in the factory production line area. Piping systems also present the designer of the booth structure with an undesirable choice of alternatives. Large piping, which can deliver water at low velocity and consequently low losses, is expensive. Smaller piping must necessarily utilize higher flow velocity, with consequent increase in losses. High-volume and low-velocity pumps are also necessarily larger and usually more expensive than the smaller units capable of producing the same valume of water at correspondingly higher velocities. High pressure systems, which may be permitted to utilize less expensive piping and smaller pumps, necessarily involve greater pressures, and pumps capable of handling these pressures are prone to maintenance difficulties with regard to seals and wear. The higher velocities associated with the smaller pipes must necessarily utilize various velocity-retarding devices to prevent the water supplied to the water-curtain panels from producing unequal distribution of the water.

The control of the discharge of water from supply troughs to the panels supporting the curtains has usually been provided by the use of a metering slot in the bottom of the trough. and these have been prone to become clogged with paint particles. Even though the water in the system is recirculated from the sump through some sort of filtration arrangement, removal of the particles is never 100 percent effective.'Once the metering slots become clogged, the water curtain becomes deficient in this area. Paint then becomes lodged on the panel normally supporting the water curtain, requiring expensive manual cleaning operations. The same is true when the troughs are replaced by nozzles, as these become clogged in the same manner.

Conventional forms of spray booth structures are usually provided with completely separate exhaust and pumping systems. These obviously require a plurality of motors, together with the associated wiring and control systems. The cost of this arrangement is aggravated in spray booth structures by the necesity that allsuch electrical installations be explosion proof.

Production line spray booths are usually equipped with some form of automated spray-gun systems,.which can be fixed, rotary, or mounted on a carriage having linear movement. Particularly in the latter case, drive mechanisms are responsible for a very substantial part of total cost of the spray gun installation. In order to utilize relatively small motors, speed reducers of some form are employed, and the cost of the power system must therefore include both that of the motor and the speed-reducer.

SUMMARY OF THE INVENTION A water-wash system is provided by the present invention with the objectives of increasing the efficiency of the water distribution, and at the same reducing both cost of the installed equipment and its maintenance. The flow of water in the booth structure is induced by a water lift operating at a high volume and low pressure, the water subject to the lift operation being preferably exposed to the local atmospheric pressure so that the liquid pressure is a function entirely of the height of the head of the liquid, to exclusion of additional pressures normally associated with confinement of the liquid within piping. Water elevated by the lift is distributed laterally to troughs by the effect of gravity, and the troughs deliver this water to the associated water-curtain panels exclusively by overflow, rather than through metering slots. The bottom of the trough is continually purged by a maintenance of flow along the bottom induced by the presence of openings at the opposite ends of the troughs. The sump of the spray booth structure, from which the water lift draws its supply. is provided with a filtering screen disposed at a position within the sump such that an induced circulation favors the sweeping of the filter screen clear of particles, which are carried to a position in the sump which is relatively stagnant to permit settle-out. This sump circulation is induced by the relative placement of panels carrying primary and secondary water curtains so that the drainage is deposited at positions appropriate for generating the desired circulation. The structure of the booth is simplified by providing the trough supplying the primary water curtain with an air seal so that the trough can also be exposed behind this panel to reduced pressure induced by the exhaust system. The troughs are also preferably equipped with baffle assemblies readily insertable and removable from the troughs through adjacent access doors or panels.

The configuration of the booth is such as to accept readily detachable spray gun modules, which normally contain automated or fixed spray systems associated with a particular production run. The detachment of a module from the remaining booth structure places this structure in a condition such that it can be used in connection with manual spray operation on articles carried by a conveyor past the front area of the booth. Where the modules use a carriage with linear movement, a drive mechanism is provided by this invention which utilizes a differential system involving a chain drive, and producing a speed reduction while eliminating the cost of the usual speed reducer.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a front perspective view of a spray booth embodying the invention, with a spray gun module attached in operating position.

FIG. 2 is a front perspective view of the assembly shown in FIG. 1, showing the spray gun carriage in a central position on its guideway.

FIG. 3 is a top view of the machine as shown in FIG. 2.

12-12 of FIG. 13;

FIG. 13 is a fragmentary horizontal section on the plane 13-13 of FIG. 12.

FIG. 14 is a sectional elevation on the plane 14-14 of FIG. 13.

FIG. 15 is a sectional view on the plane 15-15 of FIG. 14, on an enlarged scale.

FIG. 16 is an enlarged view in side elevation showing the lower extremities of the water lift assembly.

FIG. 17 is a perspective view showing the water lift assembly and the distribution troughs.

FIG. 18 is a perspective view of the air seal plate incorporated in the upper trough.

FIG. 19 is a perspective view showing the deformable valve plate for controlling the supply to the lower trough.

FIG. 20 is a perspective view of the diverter incorporated in the lower trough at the point at which it receives water from the water lift assembly.

FIG. 21 is a perspective view of the lower bearing support for the propellor shaft of the water lift assem- FIG. 22 is a perspective view on an enlarged scale showing the support post assembly carrying the unit shown in FIG. 21.

FIG. 23 is a front perspective view of the spray module illustrated in FIG. 1.

FIG. 24 is a rear perspective view of the spray module shown in FIG. 23.

FIG. 25 is an end elevation on an enlarged scale of the upper portion of the spray module.

FIG. 26 is a section on the plane 26-26 of FIG. 25, showing the right-hand portion of the machine as viewed in FIG. 23.

FIG. 27 is a section on the plane 26-26 of FIG. 25 showing the left-hand portion of the machine as viewed in FIG. 23.

FIG. 28 is an end view on an enlarged scale on the plane 28-28 of FIG. 27.

FIG. 29 is a top view of the spray gun carriage on an enlarged scale over that of FIG. 23, with part of the i the chain omitted.

FIG. 32 is a fragmentary sectional view on an enlarged scale over that of FIG. 31, on the plane 32-32 of FIG. 29.

FIG. 33 is a section on the plane 33-33 of FIG. 29 on an enlarged scale.

FIG. 34 illustrates a spray booth assembly of the type shown in FIG. 1, equipped with a rotary device for cycling objects to be painted to and from the working area of the spray booth.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The assembly shown in FIG. 1' includes the basic spray booth unit indicated generally at 50 to which the spray gun module 51 has been added. This latter unit includes a carriage 52 supported on the guide rails 53 and 54. A variety of spray gun units (not shown) will normally be mounted on the carriage 52, according to the needs of the particular spraying operation to be performed. The module 51 is detachably secured to the basic booth 50, with the result that a change in production requirements from one type of spraying operation to another can be accomodated very quickly by removal of the module 51, and replacing it with a different module provided with spray gun arrangements and programming appropriate to the new requirements. Each of these modules has a control panel 55 associated with the equipment mounted in the module. The module 51 joins with the basic spray booth 50 on a plane of separation indicated at 56 preferably just in front of the water-curtain panel 57, which is part of the structure of the basic booth 50. The end panels 58a and 58b of the module 51 form continuations of the sides 59 and 60, respectively, of the basic booth, so that the sides and top of the module define the uppeer portion of a work opening directly opposite the water curtain panel 57. It is significant that the removal of the module SI produces a configuration which is useful in a situation where a conveyorizedproduction line may be carrying articles to be painted by hand-held spray guns. Referring to FIG. 6, the path of the conveyorized articles can be appropriately established to move directly above the offsets 61 and 62, so that the ariicles sprayed pass in close proximity to the water curtain panel 57. This arrangement assures that any droplets of paint from the conveyorized items will be able to fall directly downward into the sump area indicated at 63 constitutingthe lower portion of the basic booth structure 50.

An exhaust system terminates in a duct 64, which is normally connected to some sort of manifold structure installed in an overhead position in a factory area, the function of the exhaust system being to induce a flow inward in the opening defined by the spray gun module, and from this point downward toward the surface of the water contained in the sump 63, and then underneath the lower edge of the water curtain panel 57. The exhaust draft then follows an upward path in the rear portion 65 of the booth structure, which is itself primarily a duct from which the flow is collected by the portion 66 for entrance into the duct 64. Where the booth is used in the configuration shown in FIG. 6, the effect of the induced exhaust draft will bring in air from the general frontal area around the machine from directions which will also include the opposite sides. This inflow will tend to confine sprayed particles to the portions of the machine protected by the water circulation system.

Referring particularly to FIGS. 4 and 5, the rear of the machine is provided with the access panels 67-70 covering the openings 71-74 respectively. These points of access are provided at positions convenient for performing adjustment, inspection, and cleaning operations on the interior equipment. The motor 75 is mounted on the rear of the housing, and drives a fan 76 mounted within the duct 64 through the belts 77. (Refer to FIG. 14). The shaft of the motor 75 extends downward to provide a power transfer through the belts 78 to a sheave 79 secured to the shaft 80 to provide power for the water lift system. The equipment indicated at 81-83 in FIG. 4 is associated with the control of the motor 75. The plumbing connection 84 provides for fill and drainage of the sump associated with the water-circulation system within the basic booth structure.

Referring to FIG. 7I0, modifications of the FIG. 14 drive system include the common shaft arrangement illustrated in FIG. 7, in which the motor 84 drives the shaft 85 carrying both the water lift propellor 86 and the exhaust fan 87. Power is transferred so the shaft 85 by the belt 88 through an appropriate opening in the duct 64. In FIG. 8, the motor 84 is used exclusively to drive the fan 84, while a separate motor 89 is mounted within the portion 65 of the booth structure to provide power for the shaft 80 of the water lift system. In FIG. 9, the arrangement is similar to that of FIG. 8, except that the motor 89 is mounted exteriorly of the housing of the booth. For comparison purposes, FIG. illustrates schematically the arrangement'shown in greater detail in FIG. 14. The belt guard 90 shown in FIG. 14 is not shown in either FIG. 10 or in FIG. 5.

The water-circulating system appears most clearly in FIGS. 12 thru 16. The water level in the sump 63 is indicated at 91. The circulation of water indicated in FIGS. 12 and 14 is established by the water lift assembly shown in FIG. 17. The lower extremity of this assembly is aligned by a structure including the base plate 92 secured to the floor 93 of the sump. A group of three screws 94 traverses the base plate 92, and are welded in position to form studs projecting upward above the plate 92 for engagement with the spacers 95. These spacers are essentially drilled rods with a central hexagonal portion 96 for receiving a wrench. The internal threading at the opposite ends of the spacers 95 receives the screws 94, and also the bolts 97 securing the upper plate 98 with respect to the base plate 92 at 3 points. All three of these space assemblies are identical. The plate 98 has a round central opening receiving the cylindrical portion 99 of an adapter extending upward to the square riser conduit 100. The portion 99 enters into the conduit 100, and the flange 101 carrying the sealing gasket 102 bears against the bottom of the conduit 100 to seal off the transition between the cylindrical and rectangular portions. The vertical placement of the flange 101 and the gasket 102 is determined by the adjustable supports provided by the bolts 103 and the lock nuts 104 and 105. The bolts 103 traverse the plate 98, with the lock nuts 104 and 105 locking the adjusted position of the bolts 103 to assure the desired placement of the flange 101. The lower extremity of the cylindrical portion 99 enters into the offset 106 in the member 107. This member provides a central bearing 108 positioned by the radial arms 109-111. Preferably, the central hub 108 will have a replaceable bearing insert 112, which will receive the water lift shaft 80 at a point below propellor 86. The member 107 is received within the central opening in the plate 98, and is secured directly to the plate 98. The bearing structure and the propellor may be serviced by providing vertical clearance through readjustment of the bolts 103, establishing sufficient space to move the plate laterally after removal of the bolts 97.

Operation of the motor rotates the shaft at a rate appropriate to cause the propellor 86 to lift water within the conduit from the level 91 of the sump upward to the outlet ports 113 on the rear face of the conduit 100 and the outlet ports 114 on the front face. The rear outlet ports 113 cause water within the conduit 100 to spill out into the auxiliary conduit 115, which is a U-shaped member extending along the square conduit 100, and secured to its sides. The upper extremity of the auxiliary conduit 115 is open, and the lower extremity is provided with the deformable control plate 116. This plate functions as a valve to control the distribution of outflow between the lower trough 117 and the upper trough 118. Expansion of the angle of the control plate 116 (shown in FIG. 19) will close off the opening through which the contents of the auxiliary conduit 15 are dumped into the trough 117, thus raising the head of water within the auxiliary conduit. This auxiliary conduit thus acts as an accumulator, and the independant head of water within it functions as an air seal keeping air turbulence out of the conduit 115 so that the flow is not distorted. Water is dumped out of the opening determined by the valve plate 116 into the trough at a point occupied by the diverter unit 119 shown in FIG. 20. Flow is thus distributed laterally in both directions into the trough 117, the lateral velocity of which is slowed by the presence of the baffle assemblies 120. These assemblies include a central rod 121 to which groups of large washers 122 are secured in spaced relationship along the length of the rod 121. This assembly is readily insertable and removable in the trough 117 for purposes of cleaning.

Water moving upward from the conduit 110 which does not discharge through the rear ports 113 is spilled out through the ports 114 into the front auxiliary conduit 123. The discharge through the bottom of this conduit is deposited in the upper trough 118. A baffle unit is also inserted in the upper trough l8, and this unit is formed by the parallel rods 124 and 124 transversing spaced pairs of washers as shown at 126 in FIG. 17, with these components being welded to form a unitary sub-assembly readily insertable and removable from the trough 118. Referring to FIG. 12, it will be noted that the trough 118 has an overflow edge from which water is spilled out over the water curtain panel 57. The opposite side of the trough 118 is open to the local pressure within the exhaust duct 65. The very substantial difference in air pressure requires the presence of the seal plate 127 shown in FIG. 18. This plate is offset to provide a flange 128 secured to the front panel 129 of the duct 65, with the illustrated offset in the plate 127 placing the lower extremity of this plate within the trough 118, and extending to a point well below the edge of the trough which spills over on to the watercurtain panel 57. The lower trough 117 spills over its edge 118 onto the inclined panel 130.

Drainage from both panel 130 and the water-curtain panel 57 moves downward toward the sump, and falls into the high-velocity exhaust air stream to form scrubbing screens tending to engage any particles entrained in the air flow with droplets of water. Referring particularly to FIG. 12, one screen of these droplets may be considered as moving downward from the lower edge of the water-curtain panel 57 and its rearwardly inclined lower extremity 131 toward the surface 91 of the water within the sump. A second screen of droplets is formed by drainage cascading down along rear surface of the water-curtain panel 57, which represents collections from the panel 130 and the various moistureremoval baffles 132-136 interposed within the duct 65 to establish a serpentine path of flow for the exhaust stream. Entrained particles of water impinged on these baffles, and accumulate sufficient size to drop back within the flow to produce a drainage supplementing the flow from the inclined panel 130. The primary flow descending along the inclined panel 130 forms a major scrubbing screen as this water drops in large volume across the flow of exhaust air. The relative placement and attitudes of the panel 130 and the inclined lower extremity of the water-curtain panel 57, produce a rotary clockwise turbulence in the sump 63, as viewed in FIG. 12.

The water is thus recycled between the various scrubbing areas. but the droplets eventually find their way down to the sump 63 at a rate corresponding to continuous recirculation of the Water within the sump. This recirculated water is continually purged by the circulation pattern within the sump, and also by a filtration system. The filter screen 137 is supported by the inclined plate 138 secured at its front edge to the bottom of the sump, and at its rear edge to the fixed rail 139. A rail 140 extends along the plate 138 to receive the lower edge of the screen 137, and provide a partial seal at this junction. The sides of the screen are supported by the abutments 141a and 141b, and the lateral position of the screen 137 is established by the guide rails 141c and 141d. The handle 142 of the screen is accessible through the opening normally covered by the panel 69. The deflector plate 143 is hinged at 144 to the duct structure, and seals off the upper edge of the screen to eliminate the need for a gasket under the panel 69 by deflecting the high-velocity flow away from the panel 69.

Water flow moving downward in front of the screen 137 tends to sweep the screen clear of particle accumulation. This material is carried forward along the bottom 145 of the sump at decreasing flow velocity; and accumulates at the front where the water is relatively stagnant. The surface water in the sump is continually moving to the rear in this flow pattern, and thus immediately subjects the deposited particles to the purging circulation. Water passing through the screen 137 enters the passage 146 communicating with the intake of the water lift system.

The spray module 51 is shown as a complete assembly in FIGS. 23 and 24. The end panels 58a and 58b of the module are stiffened by the vertical rails 147-148 and 149-150, respectively, and by horizontal rails as shown at 151 and 152 in FIG. 1. Mounting plates 153 and 154 are secured to the rails 147-150 by appropriate screws, and support the opposite ends of the carriage guideway and the carriage drive system. The carriage 52 will normally contain a variety of spray gun installations, which are selected and adjusted to suit the needs of the particular spraying operation underway. The carriage will also be connected to the fixed booth structure by conventional flexible conduits supplying compressed air and painting material to the spray gun installation. The tubing connections to the carriage are shown in FIG. 25, and the interrelation of these with the controls and gauges on the panel 55 is illustrated in FIG. 24. These fluid and air connections are conventional. and form no part of the present invention. They are illustrated merely as exemplary of a practically infinite variety of arrangements of standard catalog components. Some of these components may be mounted on the cover panel 155, as shown in FIG. 24, which is hinged to the structure supporting the front panel 55 as indicated at 156. FIG. 24 shows the cover panel swung down for access to the components.

The carriage structure and its drive mechanism are illustrated in FIG. 25-31. The structure shown in FIG. 29 may be considered the chassis of the carriage, the fixed portion of which includes the opposite side rails 157 and 158 separated by the spacer rods 159 and 160. Pillow-block bearings as shown at 161 in FIG. 29 are installed at the four corners of the frame established by the members 157-160, for supporting the shafts 162 and .163. The V rollers 164 and 165 are secured directly to the shaft 162 and 163 respectively, and the opposite rollers 166 and 167 are installed with a slip fit permitting a degree of axial shifting of these latter rollers with respect to the rollers 164 and 165. This arrangement accomodates minor deviations in parallelism between the tubular guide rails 53 and 54, which are engaged by the rollers 164'and 165, which are axially fixed with respect to the side rail 157, and consequently are responsible for the lateral placement of the carriage with respect to the guide rails. This axial placement may be determined by collars as shown in 168 and 169 in FIG. 29, and by control of the end-play between the components between these collars.

The plate 170 is mounted on the front of the carriage frame rail 158, which supports a stub shaft 171 carrying the retaining roller 172. This roller engages the under side of the rail 53, and holds the rollers 166 and 167 in solid engagement with this rail. On the opposite'side of the carriage, the plate 173 carries a similar assembly including the stub shaft 174 and its retaining roller 175. This latter roller maintains the engagement of the rollers 164 and 165 with the guide rail 154.

The plate 173 extends upwardly to form a part of a bracket supporting the fixed stub shafts 176-178. The shafts 176 and 178 rotatably support the idler sprocket 179-180 and 181-182, respectively. The shaft 177 carries a unitary sprocket assembly including a central hub 183, a smaller sprocket 184, and a larger sprocket 185. These two sprockets are adapted to receive the same endless chain 186, and are consequently provided with teeth of the same pitch. Obviously, the sprocket 184 will have fewer teeth than the sprocket 185. It is preferable to incorporate the additional plate 173a in the assembly, which is secured to the stub shafts 176-178 by screws as shown at 187-189 in FIG. 29. The cover 190 not only protects the sprockets, but provides a degree of shear transfer between the plates 173 and 173a.

The assembly described above constitutes a differential arrangement best illustrated in FIG. 30. The chain 186 has the upper course 191 engaging the underside of the larger sprocket 185, and the lower course 192 engaging the upper side of the smaller sprocket 184. The two courses 191 and 192 are laterally displaced by the distance between the sprocket 179-180 (which is the same as the distance between the sprockets 184 and This out-of-plane relationship between the courses 191 and 192 is accommodated by the inclined drive mechanism shown in FIGS. 25 and 28. The motor 193 is mounted on a bracket 194 secured to the plate 154,

and the motor sprocket 195 drives the endless chain 186 through the openings 1% and 197 in the plate 154. The incline of the axis of the motor 193 places the upper and lower tangents of the sprocket 195 in a sufficiently laterally-displaced position to accommodate the placement of the chain established by the carriage sprockets. At the opposite end of the module from the motor 193, an idler sprocket 198 is rotatably mounted on a shaft 199 carried by a U-shaped bracket 200. This bracket is secured by the nuts 201 and 202 to bolts traversing the plate 153. The springs 203 and 204 are interposed between the heads 205 and 206 of these bolts the washers 207 and 208 to establish a biasing action pulling the bracket 200 continually to the left, and thus maintain an adjusted tension in the chain 186. As shown in FIG. 28, the placement of the holes in the end plate 153 receiving the bolts results in an inclined placement of the bracket 200, maintaining the lateral displacement of the courses 191 and 192 of the chain.

Referring to FIG. 30, it is obvious that chain courses 191 and 192 will be moving in opposite directions at the same velocity. It is also obvious that the sprockets 184 and 185 are rotating at the same angular velocity, by a virtue of being rotatively interconnected. The differences in the diameters of the sprockets 184 and 185 will therefore cause a movement of the carriage to the right or left, whenever the chain 186 is moved by motor 193, depending upon the direction of rotation of the motor. To look at this mechanism in a slightly different way, the same linear chain velocity is applied to the central sprocket assembly at two different radial distances from the axis of rotation. This relationship will result in different tangential velocities of the chain with respect to the sprocket assembly. and this difference must be provided by movement of the carriage. The spray guns attached to the rails 157 and 158 at the spaced mounting holes 209 and 210, respectively, will thus be moved to and fro along a predetermined path by appropriate control of the motor 193. During this movement ofthe carriage, the helically coiled conduits 211-214 remain in communication with the carriage, and are preferably supported by cables or rods 215-219 extending between plates 153 and 154.

F IG. 24 shows one of several possible automated arrangements utilizing the spray booth structure shown in FIG. 1. The fixture 220 is mounted on the vertical shaft 221 for supporting articles to be sprayed. The shaft 221 is rotated by the motor unit 222 mounted on the stand 223. The placement of the axis of the shaft 221 is such that articles placed on the left portion of the fixture 220 (as viewed in FIG. 34) are rotated into the the spray space by the rotation of the shaft 221 180 by the motor 222. Articles previously placed on the opposite side of the fixture 220 are unloaded and replaced by other articles while the spraying operation proceeds.

I claim:

1. A spray booth having a housing, substantially vertical water-curtain panel means, a sump disposed below said panel means, trough means adjacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement comprises:

water-lift means included in said water-supply means and communicating with said sump, said water-lift means being adapted to deliver water to said trough means at local atmospheric pressure, said water-lift means including a riser conduit having at least a part thereof disposed within a portion of said exhaust duct, said water-lift means further including a propellor disposed adjacent said sump and within said conduit, and motor means operative to drive said propellor, said exhaust duct means including a fan disposed in said exhaust duct coaxially with said propellor. 2. A structure as defined in claim 1, wherein said propellor and fan are mounted on common shaft means. 3. A spray booth having a housing, substantially vertical water-curtain panel means, a sump disposed below said panel means, trough means adajacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement comprises:

water-lift means included in said water-supply means and communicating with said sump, said water-lift means being adapted to deliver water to said trough means at local atmospheric pressure, said trough means being adapted to discharge exclusively overflow to said panel means, said trough means further having a purging opening adjacent the bottom thereof. 4. A structure as defined in claim 3, wherein said trough means has purging openings at the opposite ends thereof, and said water-supply means delivers water to said trough means at an intermediate position along the length thereof.

5. A spray booth having a housing, substantially vertical water-curtain panel means, a sump disposed below said panel means, trough means adjacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement comprises:

water-lift means included in said water-supply means and communicating with said sump, said water-lift means being adapted to deliver water to said trough means at local atmospheric pressure; and

baffle means having a plurality of spaced transverse baffle members interconnected by rod means to form an assembly insertable in and removeable from said trough means.

6. A structure as defined in claim 5, wherein said housing is provided with access openings opposite said trough means.

7. A spray booth having a housing, substantially vertical water-curtain panel means, a sump disposed below said panel means, trough means adjacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement comprises: Water-lift means included in said water-supply means and communicating with said sump, said waterlift means being adapted to deliver water to said trough 

1. A spray booth having a housing, substantially vertical watercurtain panel means, a sump disposed below said panel means, trough means adjacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement coMprises: water-lift means included in said water-supply means and communicating with said sump, said water-lift means being adapted to deliver water to said trough means at local atmospheric pressure, said water-lift means including a riser conduit having at least a part thereof disposed within a portion of said exhaust duct, said water-lift means further including a propellor disposed adjacent said sump and within said conduit, and motor means operative to drive said propellor, said exhaust duct means including a fan disposed in said exhaust duct coaxially with said propellor.
 2. A structure as defined in claim 1, wherein said propellor and fan are mounted on common shaft means.
 3. A spray booth having a housing, substantially vertical water-curtain panel means, a sump disposed below said panel means, trough means adajacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement comprises: water-lift means included in said water-supply means and communicating with said sump, said water-lift means being adapted to deliver water to said trough means at local atmospheric pressure, said trough means being adapted to discharge exclusively overflow to said panel means, said trough means further having a purging opening adjacent the bottom thereof.
 4. A structure as defined in claim 3, wherein said trough means has purging openings at the opposite ends thereof, and said water-supply means delivers water to said trough means at an intermediate position along the length thereof.
 5. A spray booth having a housing, substantially vertical water-curtain panel means, a sump disposed below said panel means, trough means adjacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement comprises: water-lift means included in said water-supply means and communicating with said sump, said water-lift means being adapted to deliver water to said trough means at local atmospheric pressure; and baffle means having a plurality of spaced transverse baffle members interconnected by rod means to form an assembly insertable in and removeable from said trough means.
 6. A structure as defined in claim 5, wherein said housing is provided with access openings opposite said trough means.
 7. A spray booth having a housing, substantially vertical water-curtain panel means, a sump disposed below said panel means, trough means adjacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement comprises: water-lift means included in said water-supply means and communicating with said sump, said water-lift means being adapted to deliver water to said trough means at local atmospheric pressure, said sump having a filter screen disposed adjacent the rear of said sump and forming at least a portion of a partition therein, said water supply means communicating with said sump to the rear of said partition, and said sump receiving flow from said water-curtain panel in front of said partition.
 8. A structure as defined in claim 7, wherein said flow from said water curtain panel means is deposited at a position in said sump relatively closer to said filter screen than to the front of said sump, and the relative placement of said water-curtain panel means and filter screen is operative to maintain a substantially greater velocity of water flow across said screen than in the front area of said sump.
 9. A spray booth having a housing, substantially vertical water-curtain Panel means, a sump disposed below said panel means, trough means adjacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement comprises: water-lift means included in said water-supply means and communicating with said sump, said water-lift means being adapted to deliver water to said trough means at local atmospheric pressure; and second trough means, said second trough means being disposed in said exhaust duct, and also including a baffle panel extending downward at an incline from an overflow edge of said second trough means and defining with said exhaust duct means a serpentine path for the flow of air upward therein.
 10. A structure as defined in claim 9, wherein said water-curtain panel has a portion at the lower extremity thereof turned toward the central portion of said exhaust duct means, said baffle panel and second trough means being disposed on the opposite side of said exhaust duct means from said water-curtain panel.
 11. A structure as defined in claim 9, wherein said water lift means has a riser conduit communicating with said sump, and also has an accumulator conduit communicating with said second trough means and with said riser conduit.
 12. A structure as defined in claim 11, additionally including an adjustable gate at the lower extremity of said auxiliary conduit.
 13. A spray booth having a housing, substantially vertical water-curtain panel means, a sump disposed below said panel means, trough means adjacent the upper margin of said panel means providing a supply of water to said panel means, exhaust duct means communicating with the space in front of said panel means, and water-supply means communicating with said trough means and said sump, wherein the improvement comprises: water-lift included in said water-supply means and communicating with said sump, said water-lift means being adapted to deliver water to said trough means at local atmospheric pressure, said trough means communicating with said exhaust duct, and having an air seal panel extending from said trough means to a level below that of the lowest edge of said trough means.
 14. A spray booth having a housing, a sump, substantially vertical water curtain means disposed to drain into said sump at an intermediate position along the front-to-rear dimension of said sump, and pump means adapted to supply water to said water-curtain means from said sump, wherein the improvement comprises: at least one spray gun module having a substantially open bottom and opposite end portions forming continuations of said housing, said end portions having vertical junctions therewith adjacent the plane of said water curtain means, said module being removably engageable with said housing.
 15. A structure as defined in claim 14, wherein the top of said module is continuous with the top of said housing, said module defining the top and sides of a work opening opposite said water curtain means. 